1. The sub will still have significant output well above 80 Hz; it is not an instantaneous roll-off; and,
2. The influence of lower (and higher) frequencies upon our hearing is known and normal. Excess bass, or a lack of bass, can affect our perception of the rest of the frequency band.
IMO - Don
"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley